Polyurethane composition containing a property-enhancing agent

ABSTRACT

A composition comprising at least a part A and a part B is disclosed. The part A comprises at least one polyol and the part B comprises at least one isocyanate. At least one part further comprises at least one of the following: a strength enhancer having a softening point of from about 120° F. to about 400° F.; a non-reactive hydrophobic enhancer; and/or an impact absorption enhancer. These enhancers provide, among optional other benefits, enhanced pull strength. Additionally, a mass can be prepared by a method of combining part A with part B and applying the mixture to a void. The compositions may also be used in the repair of surface defects or for the reinforcement of structural members such as spike holes left after spike removal from railroad ties during road bed maintenance or repair.

FIELD OF THE INVENTION

This invention relates to a composition comprising at least a part A anda part B. The part A comprises at least one polyol and the part Bcomprises at least one isocyanate. At least one part further comprisesat least one of the following: a strength enhancer having a softeningpoint of from about 120° F. to about 400° F.; a non-reactive hydrophobicenhancer; and/or an impact absorption enhancer. These enhancers provide,among optional other benefits, enhanced pull strength. Additionally, amass can be prepared by a method of combining part A with part B andapplying the mixture to a void. The composition may also be used in therepair of surface defects or for the reinforcement of structural memberssuch as spike holes left after spike removal from railroad ties duringroadbed maintenance or repair.

BACKGROUND OF THE INVENTION

Materials used to repair defects in structural members should havecertain characteristics. The material should be easily applied andshould form high strength bonds to structural members made of varyingmaterials. Particularly for outdoor repairs, the repair materials shouldbe usable in many environments including environments having extremes ofheat and cold and having the presence of substantial quantities ofenvironmental water.

One particularly important end use for such repair compositions is inthe recycle or reuse of railroad ties. Typically in the maintenance ofthe railroad right of way, the rails along with the tie plates andspikes are removed from railroad ties, which remain in the roadbed. If anew rail is to be spiked to the old tie, it is critical that therailroad tie spike holes be repaired prior to laying the new rail. Thepresence of spike holes in an old tie can cause problems since if aspike is driven into a portion of the tie near an old spike hole, thedriving force of the spike can displace the spike from its intendedlocation into an old hole, displacing the rail, tie plate and spike. Inthe instance that the spike is driven into an incorrect locationsubstantial economic loss can result in repairing the misaligned rail.If a misaligned rail is not repaired, the defect can cause derailment orother problems. Further, the spike holes can be the source of structuralweakness in the tie, allowing water to enter the core of the tieaccelerating the degradation.

The use of polyurethane foam in filling spike holes in used railroadties has come a long way, but still can present significant problems.The polyurethane foam compositions do not appear to consistently adhereto a spike hole with sufficient adhesion to prevent the accidentalremoval of the foam repair mass during the repair and subsequentmechanical rail installation. Further, most urethane foams of the priorart tended to foam uncontrollably in the presence of substantialenvironment moisture. Since moisture tends to accelerate the foamingproperties of the urethane composition, the presence of water can causetoo rapid of cell expansion resulting in a foam mass of low strength andlow density that can result in the formation of an incomplete orunreliable repair of structural members.

Various polyurethane compositions and improvements have been suggested.However, there is still a substantial need in the art for repairingcompositions that employ non-carcinogenic ingredients and that can beused to repair surface defects on structural components such as railroadties to provide a repair mass having strong adhesion to the substratestructural member and strong pulling strength, which can be used in thepresence of substantial quantities of environmental water and can beused in automatic application equipment in all temperatures.

SUMMARY OF THE INVENTION

The compositions of the present invention comprise at least a part A anda part B. The part A comprises at least one polyol and the part Bcomprises at least one isocyanate. At least one part further comprisesat least one of the following: a strength enhancer having a softeningpoint of from about 120° F. to about 400° F., a non-reactive hydrophobicenhancer, and/or an impact absorption enhancer. These enhancers provide,among optional other benefits, enhanced pull strength. Methods of usingthese compositions are also disclosed.

DETAILED DESCRIPTION OF THE INVENTION I. The Compositions

The composition of the present invention comprises at least twoparts—part A and part B. Generally, each part is provided separately andmixed immediately prior to application. However, the invention alsocontemplates encapsulated ingredients which release, e.g., upon exposureto pressure and/or heat, particularly encapsulated catalysts,isocyanates and/or gelling agents. Thus, part B could be encapsulateddiscrete particles dispersed in a liquid part A (e.g. at 80 F) or viseverse. Solid particles dispersed in a liquid medium however areconsidered the same “part”. In some embodiments, the polyurethanecomposition is formulated as a foamable composition. That is, thecomposition foams, upon mixing the two parts and exposing the mixture tothe environmental pressures and temperatures. The density of thecompositions does not typically change substantially when thecomposition is cured in the wet environments in comparison to the dryenvironments. In some embodiments, the difference in the wet densityfrom the dry density is no greater than about 20 lbs./ft³ (0.32 kg/dm³)more preferably no greater than about 10 lbs./ft³ (0.16 kg/dm³)

A. Part A.: Part A of the composition comprises at least one polyol.

Polyols and methods for their preparation are known. For the purpose ofthe present invention, a “polyol” is an ingredient having at least twoactive hydrogen atoms. The term “active hydrogen atom” refers tohydrogen which displays activity according to the Zerewitnoff test asdescribed by Kohlerin, Journal of American Chemical Society, Vol. 49, pp31-81 (1927). For the purpose of the present invention, a “polyol” doesnot include water, although water may be included in the composition.Polyols are typically present in part A at from about 5% to about 100%by weight of the part. As used herein, the phrase “by weight of thepart” means that the weight percentage is based upon the weight of thepart that contains the ingredient (or in this case the polyol). In otherwords, if part A comprises the ingredient, the weight percentage of“from about 5% to about 50% by weight of the part” means from about 5%to about 50% by weight of Part A.

The polyol(s) in part A, in general, have a number average molecularweight of from about 50 to about 8000, a functionality of from about 2to about 8, and a hydroxyl number of from about 14 to about 1800, orfrom about 24 to about 500, as determined by ASTM designation E-222-67(Method B).

Useful polyols include polyethers, polyesteramides, polythioethers,polycarbonates, polyacetals, polyolefins, polysiloxanes, various gradesof caster oils, hydroxy-terminated prepolymers. Polyether polyols areused more often. Suitable polyether polyols (or polyoxyalkylene polyols)are prepared by reaction of any of the following polyhydroxy compoundswith an alkylene oxide such as ethylene oxide, 1,2-propylene oxide,1,3-propylene oxide, epichlorohydrin, epibromohydrin, 1,2-butene oxideand tetrahydrofuran. Suitable polyhydroxy compounds for reaction withthe alkylene oxides include simple aliphatic polyols such as ethyleneglycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol,tetramethylene glycol, pentamethylene glycol, hexamethylene glycol,decamethylene glycol, 2,2-dimethyltrimethylene glycol, glycerin.Trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol,1,6-hexanediol, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, castor oil,polyvinyl alcohol and partially hydrolyzed polyvinyl acetate;carbohydrates containing 5 to 8 hydroxyl groups such as sucrose,dextrose, and methylglucoside, ether polyols such as diethylene glycoland dipropylene glycol; aromatic polyols such as diphenylene glycol; andmixtures thereof are also useful. These polyether polyols includepolyethylene glycol and polytetramethylene ether glycol.

Other suitable polyols include, such as, ethylene glycol, propyleneglycol, diethylene glycol, dipropylene glycol, 1,4-butanediol,1,6-hexanediol, hydroxy terminated prepolymers, glycerol,trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol and mixturesthereof. Polyols described in U.S. Pat. No. 4,661,532, U.S. Pat. No.6,288,133 B1 and U.S. Pat. No. 6,455,605 may also be employed.

Part A of the composition may further comprise at least one thixotropicgelling agent. Any material that will thicken the mixture, particularlyat the interface that contacts the substrate or water, to the extentthat the isocyanate component is substantially prevented from reactingwith excess environmental water, is suitable for use as the thixotropicgelling agent. Preferably, any material that could provide fast orinstant thixotropic gelling reaction with the isocyanate in, such as,preferably no greater than about 5 seconds, is more suitable for theapplication of the invention. Suitable thixotropic gelling agentsinclude peroxides, polyamides, and preferably polyamines. The polyamineis typically a primary or secondary amine and present in the part Acomponent in a range from about 0.1% to about 10% by weight of the part,and preferably from about 0.5% by weight to about 5% by weight of thepart. Upon mixing the polyol and isocyanate component, the compositiontypically thixotropically gels fast within 1 minute or even within about5 seconds or less when mixed and applied by meter-mix applicationequipment.

It is surmised that in the absence of a thixotropic gelling agent, theretends to be a substantial difference in the foam density achieved at dryconditions in contrast to wet conditions. Since water is a commonblowing agent, the rate of expansion of foamable compositions typicallydirectly relates to the concentration of water present. Hence, as theconcentration of water increases, polyurethane compositions in theabsence of the thixotropic gelling agent tend to froth, rather thanproduce a consistent foam. It is also surmised that the polyamine actsas a chemical thixotrope to provide an instant thixotropic gel once thetwo parts are blended together. It is further surmised that the instantformation of a thixotropic gel, e.g., within a few seconds, enhances thesealing characteristics of the resultant foam. For example, vacant spikeholes often create voids within a railway tie that can pass completelythrough the tie. As the two parts of the foamable composition are mixingand simultaneously injecting into the hole, the fast or instantthixotropic gelling action provided by the thixotropic gelling agentsuch as polyamines, preferably, polyamines which could provide thedesired thixotropic gelling, allows the composition to more rapidlyadhere to the inner surface of the hole, as well as more adequately sealthe hole upon foaming within the void. In the absence of the appropriatethixtropic gelling agent, the composition is more likely to flow throughthe hole and/or cracks and provide an inadequate seal once foamed.Alternatively, in the absence of a thixotropic gelling agent, theingredients for each part may be selected such that the composition issufficiently high enough in viscosity upon mixing the part A with thepart B. However, this is much less desirable since the initial highviscosity causes the composition to be more difficult to applyconsistently, particularly at low application temperatures.

In the embodiments where a polyurethane foam is formed, part A may alsocomprises at least one blowing agent. A common blowing agent is water,which may be present in an amount of from about 0.05% by weight to about1% by weight of the part or even 0.15% to 0.5% by weight of the part. Inmany instances, the polyol(s) and/or the other ingredients in part A maycontain a small concentration of residual moisture or water that may besufficient to act as a blowing agent. Accordingly, the blowing agent maybe inherently present, and thus need not be separately added.

B. Part B: Part B of the composition of the present invention comprisesat least one isocyanate.

Any of a wide variety of organic polyisocyanates compositions may beemployed in the isocyanate component, including monomeric and/orpolymeric polyisocyanates which may be linear, branched, cyclicaliphatic polyisocyanates, cycloaliphatic polyisocyanates, aromaticpolyisocyanates, isocyanate-terminated prepolymers, isocyanurates andmixtures thereof. Representative examples include 2,4-toluenediisocyanate (TDI), diphenyl methane diisocyanate (MDI), m-phenylenediisocyanate, 4-chlor-1,3-phenylene diisocyanate, 4,4′-biphenyldiisocyanate, 1,5-naphthalene diisocyanate, 1,4-tetramethylenediisocyanate, 6-hexamethylene diisocyanate, 1,10-decamethylenediisocyanate, 1,10 decamethylene diisocyanate, 1,4-cyclohexylenediisocyanate, 4,4′-methylene-bis(cyclohexyl isocyanate) and others.Further, the isocyanate compound may contain other substituents that donot substantially detract from the reactive natures of the isocyanategroups. In some embodiments, a blend of two or more isocyanates whereinat least one of the isocyanates is aromatic may be employed. Aromaticdiisocyanates, those that have at least two isocyanate groups directlyattached to an aromatic ring, react in the urethane reaction morerapidly with polyols than the aliphatic isocyanates. Some otherparticularly useful isocyanates are polymeric MDIs s includingpolymethylene polyphenyl isocyanates containing 4,4′methylene bisphenylisocyanate commercially available from The Dow Chemical Company,Midland, Mich. as PAPI 27, PAPI 20 and PAPI 94; from Huntsman asRubinate M, Rubinate 9257, and Rubinate 9258; and from Bayer as ModurMR, MR-200 and MRS-10. Isocyanates described in U.S. Pat. No. 4,661,532,U.S. Pat. No. 6,288,133 B1, and U.S. Pat. No. 6,455,605 may also beemployed.

Isocyanate-terminated prepolymers can also be used.Isocyanate-terminated prepolymers are known from U.S. Pat. Nos.3,073,802 and 3,054,755 and are generally prepared by reacting an excessof polyisocyanates, such as an aromatic diisocyanate with polyalkyleneether glycols, or polyester glycols. The isocyanate can also be used inthe form of a blocked isocyanate.

The isocyanate is present in part B in an amount of up to about 100% byweight of the part. In some embodiments, the isocyanate is employed at aconcentration from about 50% to about 95% by weight of the part, and inother embodiments, from about 70% to about 90% by weight of the part.

C. Optional Ingredients: Part A and/or part B of the composition mayfurther comprises at least one diluent to reduce the viscosity of thecomposition, thereby enhancing the flow characteristics, especiallyduring the railroad tie repair operation. Suitable diluents includepolymeric resins, elastomers, waxes, oils and mixtures thereof. Specificexamples include phthalate esters, alkyl phosphates, polyphenyls, di-and triphenyl compounds as well as partially hydrogenated versions,aromatic oils, chlorinated waxes or paraffins, adipate esters, syntheticrubber polymer, natural oils, rosin and rosin derivatives, andpolysulfide rubber. One of ordinary skill in the art will readilyrecognize that, e.g., synthetic rubber polymers that are useful asdiluents are not the same as those synthetic rubber polymers useful asenhancers in the present invention. A key difference readily apparent isthe viscosity of the synthetic rubber polymers as their viscositydirectly impacts the viscosity of the part. One diluent is Eastman TXIBPlasticizer, which is 2,2,4-trimethyl-1,3-pentanediol diisobutyrate fromEastman Chemical Company (Kingsport, Tenn.). The diluent may be presentin either part in a range of from about 1% to about 50% by weight of thepart, and may be from about 5% to about 20% by weight of the part.

Advantageously, the ingredients may be selected to lower thecrystallization temperature of each of part A and/or part B componentsto improve the freeze-thaw stability. For example, the railroad industryrepairs tracks year round, and fluctuations in temperature, especiallyduring low temperatures, prefer that each part flow without additionalheat at reduced temperatures. Additionally, the isocyanate used in thepart B component may tend to crystallize under cooler temperatures sothe addition of a diluent allows enhanced processing characteristics.

Part A and/or part B of the composition may further comprise at leastone catalyst. The reaction rate of part A with part B can be acceleratedby incorporating an effective amount of at least one catalyst thatpromotes the active hydrogen atom/isocyanate reaction. Suitablecatalysts are those known to enhance the polyol/isocyanate reaction,water/isocyanate reaction, urethane/isocyanate reaction andurea/isocyanate reaction. In some embodiments, a combination of thecatalysts is employed to accelerate the formation of the urethanelinkages as well as the isocyanurate linkages. Applicants surmise thatthe final cured product is comprised of a variety of linkages includingisocyanurate, biuret and urea linkages rather than predominantlyurethane linkages when using a combination of the catalysts. If present,the amount of catalyst(s) may be from about 0.1% by weight to about 5%by weight of the part, or from about 0.3% by weight to about 3% byweight of the part. Further, catalysts may be employed in combinationwith various accelerators and/or curing agents such as Lewis Basecatalysts including, e.g., ANCAMINE K.54 (Pacific Anchor ChemicalCorporation, Los Angeles, Calif.), a tris-(dimethylaminomethyl) phenol.Other useful catalysts include organic amine compounds and organometallic compounds and mixtures thereof. The amine based catalystsdiffer from the polyamine gelling agent with respect to the number ofreactive sites present in the molecule as well as to the concentrationemployed.

Whereas amine based catalysts are typically tertiary amines, thepolyamine gelling agent is typically a primary or secondary amine.

Specific examples of useful catalysts to promote the urethane reactioninclude dibutyltindilaurate, stannous octoate, tertiary aliphatic andtertiary alicyclic amines including triethylamine, triethanolamine,tri-n-butylamine, triethylenediamine, alkylmorpholene, etc. Complexmixtures of such catalysts and modified forms may also be employed.

For the promotion of the isocyanurate reaction, specific types ofcatalysts are used such as Polycat 41(N,N,N′,N′,N″,N″-hexamethyl-1,3,5-triazine 1,3,5 (2H, 4H, 6Htripropanamine), Polycat 43 (a proprietary tertiary amine) and variouscatalysts based on potassium salts of organic acids including DABCO T-45(potassium octonate in dipropylene glycol (DPB) (60/40), DABCO K-15(potassium octonate in DPG (70/30), METACURE T-120 (organo tin catalyst(17.5% tin) exhibiting high catalytic activity), and Polycat 46(potassium acetate in ethylene glycol). The Polycat and DABCO catalystsare available from Air Products & Chemicals, Inc. (Allentown, Pa.). Mostpreferred are combinations of isocyanurate reaction catalysts. Forexample, a slower reacting trimer catalyst such as DABCO TMR-2 and DABCOTMR-3 (quaternary ammonium salts) and DABCO TMR-30(2,4,6-tris(dimethylaminomethyl)phenol) may be employed and preferablyin combination with a stronger trimer catalyst. Alternatively,combinations of suitable strong trimer catalysts and a small amount ofurethane catalyst, such as DABCO 33 LV (triethylene diamine in DPG(33/67) and a metal based catalyst like DABCO T-12 (dibutyltindilaurate) may also be employed. These catalyst systems are preferred tominimize initial foaming as described in U.S. Pat. No. 5,556,934 issuedSep. 17, 1996.

II. Property Enhancing Agents

The compositions of the present invention also comprise at least oneproperty-enhancing agent in at least one of the parts. As used herein,the phrase “in at least one of the parts” means that the propertyenhancing agent may be found in part A, in part B, or in both parts. Thephrase “property-enhancing agent” refers to strength enhancers,non-reactive hydrophobic enhancers, and/or impact absorption enhancers.As used herein, the term “enhancer”, when used without a precedingadjective, refers to strength enhancers, non-reactive hydrophobicstrength enhancers, and/or impact absorption enhancers. As will bediscussed in greater detail below, these enhancers have been found toimpart beneficial properties such as increased pull strength andsometimes hydrophobicity and/or increased impact absorption.

A. Strength Enhancers: The compositions of the present invention maycomprise a strength enhancer in at least one of the parts. It has beenfound that particularly useful strength enhancers have a softening pointof from about 120° F. (49° C.) to about 400° F. (204° C.) or even fromabout 140° F. (60° C.) to about 300° F. (149° C.). As used herein, thephrase “softening point” is defined as stated in ASTM D6493-99. Notwishing to be bound in theory, it is believed that when the compositionsof the present invention are used for applications such as rail road tierepair, the heat generated from driving a spike into the hole pluggedwith the compositions of the present invention causes these strengthenhancers to melt to a degree and re-fuse, resulting in better pullstrength. The term “pull strength” as used herein refers, in general tothe quality of the bond between the compositions of the presentinvention and the structure(s) with which they interface.Quantitatively, the pull strength can be measured by one of the pullstrength tests, which are described in greater detail in the TestMethods section below. Particularly useful strength enhancers typicallyexhibit pull strengths from at least about 1000 or at least about 1200or even 1400 pounds according to the Pull Strength Test Method A.Strength enhancers useful in the present invention include but are notlimited to asphalt, PVC resins, natural and synthetic rubbers andthermoplastic polyurethane resins. The term “asphalt” as used hereinrefers to solid or semi-solid natural or mechanical mixtures of bitumenobtained from native deposits or as petroleum byproducts. Specificexamples include gilsonite, glance pitch and grahamite. “Asphalt” doesnot encompass bitumen that is obtained by distillation from coal, which,in addition to other problems, often includes carcinogens. The strengthenhancers useful in the present invention are solid or semi-solid at 80°F. in order to exhibit the desired pull strength characteristics. Thestrength enhancers are dispersed in at least one of the parts. Strengthenhancers may be included at from about 5% to about 50% by weight of thepart, or even from about 10% to about 30% by weight of the part.

One of ordinary skill in the art will readily recognize that thesoftening points of these ingredients may vary depending upon theirsource. For example two sources of gilsonite have different softeningpoints. Zecol LLMP available from Ziegler Chemical and MineralCorporation has a softening point range of 248° F. to 290° F. whileLexco multipurpose grade from Lexco has a softening point of 330° F. to350° F. Thus, when formulating with pull strength as a key criteria, itis recommended that the softening points mentioned above are targeted.However, as will be seen below, these enhancers may be useful in thepresent invention even when their softening points do not meet theselimitations when one considers an ancillary beneficial property theenhancer brings to the compositions. In those situations where thesoftening points are not met, other criteria will be met.

B. Non-reactive hydrophobic enhancers. The strength enhancers mentionedabove in section A may or may not have some additional desirablehydrophobic characteristics. Similarly, the non-reactive hydrophobicenhancers useful in the present invention may or may not meet thesoftening point criteria set forth in section A. Nevertheless, they docontribute to improved pull strengths of the final compositions and,moreover, have added benefits of hydrophobicity which results in moreresilient, better performing compositions. These hydrophobiccharacteristics are particularly useful when dealing in situations wherethere may be an abundance of water or moisture. For example, vacantspike holes often contain pooled water, which increases the foaming anddecreases the density, which can be detrimental. Additionally, thesenon-reactive hydrophobic enhancers do not detrimentally react chemicallywith other components in the system and therefore result in more stableindividual parts. Thus, “non-reactive” means that the enhancer does notsubstantially react chemically with other components in the part therebydetrimentally affecting the stability of the part. Thus, it has beenfound that the use of enhancers which are also non-reactive andhydrophobic (“non-reactive hydrophobic enhancers”) results incompositions having increased hydrophobicity which are stable and lesslikely to emulsify, absorb, and/or entrap water which can result inreducing the materials' density, rigidity and adhesion characteristics.“Hydrophobic” refers to those enhancers having a concentration of waterat ambient temperature of less than 1% after being conditioned for 14days at 100° F. (38° C.) and 95% relative humidity in a cylindricalcontainer about 4 cm in height having an inside diameter of about 3 cm.Examples of non-reactive hydrophobic enhancers include but are notlimited to asphalt such as gilsonite and some hydrocarbon resins. Whenused, the non-reactive hydrophobic enhancers are included at from about1% to about 50% by weight of the part, or even from about 5% to about30% by weight of the part.

C. Impact absorption enhancers. The strength enhancers mentioned abovein section A may or may not have some additional desirable impactabsorption characteristics. Similarly, the impact absorption enhancersuseful in the present invention may or may not meet the softening pointcriteria set forth in section A, yet they do contribute to improved pullstrengths of the final compositions and, moreover, have additionalbenefits of impact absorption which may be useful in some applications.The ability of the composition to absorb some vibrations or occasionaljolts may preserve existing bonds between the structure and thecompositions which otherwise would weaken the overall system and “true”pull strengths in a real setting. The phrase “impact absorptionenhancers” refer to enhancers that improve pull strengths and providedesirable impact absorption characteristics. It is important that the“impact absorption enhancers” do not reduce the viscosity of the partthey are incorporated in nor the viscosity of the final composition asit has been found that reducing viscosity generally diminishes thedesired characteristics. Thus, the “impact absorption enhancers” usedherein often have viscosities themselves of more than about 100,000centipoises (cps). Specific examples of useful impact absorptionenhancers include but are not limited to PVC, ground rubber, and glassor polymeric microspheres that do not reduce the viscosities asmentioned above. When used, the impact absorption enhancers are includedat from about 1% to about 30% by weight of the part, or even from about5% to about 10% by weight of the part.

Other characteristics of the polyurethane composition of the presentinvention can be modified with commonly used additives includingfillers, extenders, ultraviolet (UV) stabilizers, antioxidants,fungicides, bactericides, surfactants, dyes, and mixtures thereof.

III. Methods of Making and Using

The polyurethane compositions of the present invention can be made inaccordance with known manufacturing methods. The polyol component andisocyanate component can be individually prepared using commonlyavailable blending and mixing techniques. The composition may beeffectively mixed and applied by using an automated meter mix equipmentthat blends the two packages at an appropriate ratio. In such processes,the two parts are meter-mixed together at a ratio of active hydrogenatoms (from Part A) to isocyanate group (from Part B) in a range of fromabout 1:0.8 to about 1:4, or from about 1:0.9 to about 1:4, andpreferably at a ratio of from about 1:1 to about 1:2. Hence, excessisocyanate is usually preferred.

For repairing a railroad tie, the composition of the invention may beformulated to be foamable. During the application, the composition maybe preheated to a temperature ranging from about 60° F. (27° C.) toabout 120° F. (49° C.) and applied into the spike hole using anautomatic mixing and application unit that is part of a track repairprocess, followed by replacement of the spike plate and rail andre-spiking the assembly together.

The composition of the present invention is also useful forreinforcement of composite structural members including buildingmaterials such as doors, windows, furniture and cabinets and for welland concrete repair. The composition can be used to fill any unintendedgaps, particularly to increase the strength. Structural components areformed from a variety of materials such as wood, plastic, concrete andothers, whereas the defect to be repaired or reinforced can appear ascuts, gaps, deep holes, cracks, etc.

IV. Test Methods

A. Density or Dry Density is determined by dispensing the compositiondirectly into an empty cup of a known mass and volume at 77° F. (25°C.).

B. Wet Density is determined by the same method as the dry densityexcept the compositions is dispensed directly into a 150 ml cupcontaining 20 ml water.

C. Pull Strength Test Method A:

A one (1) inch (25.4 mm) diameter hole is filled with the appropriatepolyol/isocyanate mixture and allowed to cure for 30 minutes. A 3.5inches (89 mm) hard cut masonry nail is then pounded into the cured dryplug to a depth of 2.0 inches (50.8 mm). After one (1) hour, the nail isremoved from the plug using an Instron at a constant rate of 2.0inch/min (50.8 mm/min). The maximum force exerted during the removal isreported as the “pull strength”.

D. Pull Strength Test Method B:

A one (1) inch (25.4 mm) diameter hole is filled with the appropriatepolyol/isocyanate mixture and allowed to cure for 30 minutes. A 4.5inches (114 mm) 30D Common nail is then pounded into the cured dry plugto a depth of 2.4 inches (60 mm). After one (1) hour, the nail isremoved from the plug using an Instron at a constant rate of 2.0inch/min (50.8 mm/min). The maximum force exerted during the removal isreported as the “pull strength”.

V. Examples

The following examples were prepared in accordance with the followinggeneral procedure:

Part A of the composition is prepared by adding the polyol(s) andfiller(s), if any, to a Cowles dissolver at room temperature andagitating until the mixture is completely homogeneous. The moisturecontent of the material is then measure via Karl Fisher titration.Additional water is added, if necessary, to bring the overall moisturecontent up to the desired range. The remaining ingredients are thenadded and the mixture is agitated until the mixture is completelyhomogeneous. If a single isocyanate is employed as part B without anyfurther ingredient no additional preparation is required. In theinstances when part B also comprises other ingredient(s), e.g., PVC,diluent(s), polyols to make a pre-polymer, etc. all the ingredients areadded to a Cowles dissolver and agitated until the mixture is completelyhomogeneous.

Each part is packaged separately in an appropriate manner.

Table I represent various part A components whereas Table II representsseveral Part B components. The present invention encompasses allpossible combinations of Part A components and Part B components inaccordance with the claims. The dry/wet densities and the pull strengthwere tested upon combining the Part A component and Part B component ata 1 to 1 mix ratio by volume. TABLE I Part A Component IngredientProduct Name Chemical Description A1 A2 A3 A4 A5 Polyol Desmophen 550U¹Polyether triol 46.79 — 46.79 46.54 — Polyol Poly-G 85-29² Polyethertriol 24.0 14.0 14.0 14.0 14.0 Polyol Poly-G 30-400T² Polyether triol —46.79 — — — Polyol Carpol GP-700⁷ Polyether polyol — — — — 46.54 BlowingWater Water 0.1 0.1 0.1 0.06 0.04 Agent (target amount) Catalyst DabcoT-45³ Tertiary Amine in DPG 0.5 0.5 0.5 0.5 0.5 Catalyst Dabco 120³ TinCatalyst 0.5 0.5 0.5 0.5 0.5 Catalyst Polycat 43³ Tertiary Amine 0.7 0.70.7 0.7 0.7 Asphalt Gilsonite⁴ Natural asphalt — 10.0 10.0 10.0 10.0Filler Vicron 25-11⁵ Calcium carbonate 25.0 25.0 25.0 25.0 25.0 DefoamerFoamkill 8D⁶ Silicone 0.01 0.01 0.01 0.01 0.01 Surfactants LK-443³(proprietary) 0.5 0.5 0.5 0.5 0.5 Gelling Agent Amicure PACM³Cycloaliphatic Amine 2.0 2.0 2.0 2.25 2.25 Viscosity 1550 2850 2600 37002200 (cps at 77° F.)¹Available from Bayer Corp., Pittsburgh, PA;²Available from Arch Chemical, Inc.;³Available from Air Products and Chemicals, Inc, Allentown, PA;⁴Available from Ziegler Chemical & Mineral Corp., Jericho, NY;⁵Available from Specialty Mineral Inc., Lucerne Valley, CA;⁶Available from Crucible Chemical Co., Greenville, SC;⁷Available from Carpenter Co., Richmond, VA.

TABLE II Part B Component Ingredient Product Name Chemical DescriptionB1 B2 B3 B4 Polyol Carpol PGP-4000¹ Polyether polyol — — — 11.18 PolyolVoranol 220-110² Polyether diol — — — 4.22 Isocyanate PAPI 27² PolymericMDI 50.0 50.0 50.0 55.0 Isocyanate PAPI 94² Polymeric MDI — — — 9.6Isocyanate PAPI 20² Polymeric MDI 5.0 5.0 5.0 — Diluent EASTMAN TXIB³2,2-dimethyl-1-methylethyl)- — 20.0 15.0 15.0 1,3-propanediyl bis(2-methylpropanoate) Impact Geon 198⁴ Polyvinyl chloride — — 5.0 5.0absorption enhancer Isocyanate UR228MF⁵ MDI prepolymer 25.0 25.0 25.0 —Diluent Santisizer 261⁷ C7 to C9 alkyl benzyl 20.0 — — — phthalateViscosity (cps 1900 1425 2200 — at 77° F.)¹Available from Carpenter Co., Pasadena, TX;²Available from The Dow Chemical Company, Midland, MI;³Available from Eastman Chemical Co.;⁴Available from PolyOne Corporation;⁵Available from H.B. Fuller Company⁶Available from Ferro Corporation, Bridgeport, NJ.

Example 1

Part A1 is reacted with Part B4 resulting in a foam having a wet densityof 58 lbs, a dry density of 72 lbs./ft³, and a pull strength of about872 pounds measured according to Pull Strength Test Method A.

Example 2

Part A 2 is reacted with Part B4 resulting in a foam having a wetdensity of 70 lbs./ft³, a dry density of 73 lbs./ft³, and a pullstrength of about 1470 pounds measured according to Pull Strength TestMethod A.

Example 3

Part A3 is reacted with Part B4 resulting in a foam having a wet densityat of 65 lbs./ft³, a dry density of 73 lbs./ft³, a pull strength ofabout 1,160 pounds measured according to Pull Strength Test Method A.

Example 4

Part A4 is reacted with Part B1 resulting in a foam having a wet densityof 61 lbs./ft³, a dry density of 72 lbs./ft³, and a pull strength ofabout 384 pounds measured according to Pull Strength Test Method B.

Example 5

Part A4 is reacted with Part B2 resulting in a foam having a wet densityof 56 lbs./ft³, a dry density of 65.5 lbs./ft³ and a pull strength ofabout 271 pounds measured according to Pull Strength Test Method B.

Example 6

Part A4 is reacted with Part B3 resulting in a foam having a wet densityof 62 lbs./ft³, a dry density of 64 lbs./ft³ and a pull strength ofabout 430 pounds measured according to Pull Strength Test Method B.

Example 7

Part A5 is reacted with Part B1 resulting in a foam having a wet densityof 64 lbs./ft³, a dry density of 74 lbs./ft³, and a pull strength ofabout 419 pounds measured according to Pull Strength Test Method B.

Example 8

A railroad tie in need of repair is provided. A mixture according toExample 2 is applied to a void in the railroad tie. After allowing themixture to cure, a spike is nailed into at least a portion of the filledarea and holds.

The examples provided are not meant to limit the scope of the invention,but rather to provide detail helpful to teach one of ordinary skill inthe art how to make and use the present invention. While numerousembodiments and examples have been disclosed herein, it should beapparent that modifications can be made without departing from thespirit and scope of the invention. Therefore, the appended claims areintended to cover all such modifications that are within the scope ofthis invention. The relevant portions of all documents disclosed hereinare hereby incorporated by reference in their entirety. Reference to adocument is not to be construed as an admission that such document isprior art. The abbreviations “lbs” means pounds, “ft³” means cubic feet,“mm” is millimeters, “cm” is centimeters, “cps” is centipoises. “ml” ismilliliters.

1. A composition comprising at least a part A and a part B, the part Acomprising at least one polyol and at least one thixotropic gellingagent; and the part B comprising at least one isocyanate, wherein atleast one part further comprises at least one impact absorptionenhancer.
 2. The composition according to claim 1, wherein the impactabsorption enhancer is present in an amount of from about 1% to about30% by weight of the part.
 3. The composition according to claim 1,wherein the impact absorption enhancer comprises PVC.
 4. The compositionaccording to claim 3, wherein the part B comprises the impact absorptionenhancer.
 5. The composition of claim 1, further comprising a blowingagent, wherein the composition is foamable.
 6. The composition accordingto claim 1, wherein the impact absorption enhancer is present in anamount of from about 5% to about 30% by weight of the part.
 7. Thecomposition according to claim 1 wherein the composition exhibits a pullstrength of at least about 1400 pounds according to Pull Strength TestMethod A.
 8. The composition according to claim 1, wherein the impactabsorption enhancer has a viscosity of at least about 100,000centipoises.
 9. A composition comprising at least a part A and a part B,the part A comprising at least one polyol, and the part B comprising atleast one isocyanate, wherein a ratio of active hydrogen atoms in part Ato isocyanate group in part B is from about 1:0.9 to about 1:4, andwherein at least one part further comprises at least one impactabsorption enhancer.
 10. The composition according to claim 9, whereinthe impact absorption enhancer is present in an amount of from about 1%to about 30% by weight of the part.
 11. The composition according toclaim 9, wherein the impact absorption enhancer comprises PVC.
 12. Thecomposition according to claim 9, wherein the part B comprises theimpact absorption enhancer.
 13. The composition according to claim 9,wherein the ratio of active hydrogen atoms in part A to isocyanate groupin part B being from about 1:1 to about 1:2
 14. A method of repair orreinforcement of a structural member subject to routine vibrationscomprising the steps of: a) providing a structural member having a void;b) providing a mixture of the composition of claim 1; and c) applyingthe mixture to the void creating a filled area.
 15. The method of claim14, wherein the structural member is a railroad tie.
 16. A method ofimproving pull strength and impact absorption of a railroad tiecomprising the steps of: a) providing the railroad tie having a void; b)providing a mixture of the composition of claim 1; and c) applying themixture to the void creating a filled area.
 17. The method according toclaim 16, further comprising a step of nailing a spike into at least aportion of the filled area.
 18. A railroad tie comprising a compositionof claim
 1. 19. A railroad tie comprising a composition of claim 9.